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US5752167A - Radio propagation simulation method, wave field strength inference method and three-dimensional delay spread inference method - Google Patents

Radio propagation simulation method, wave field strength inference method and three-dimensional delay spread inference method Download PDF

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US5752167A
US5752167A US08/716,289 US71628996A US5752167A US 5752167 A US5752167 A US 5752167A US 71628996 A US71628996 A US 71628996A US 5752167 A US5752167 A US 5752167A
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wave
wave source
radio
delay
frequency
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Hitoshi Kitayoshi
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Advantest Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/02—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole
    • H01Q3/08—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole for varying two co-ordinates of the orientation

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  • the present invention relates to a method of simulating a multi-path propagation of a radio (electromagnetic) wave in premises and street spaces which is required, for example, for practical use of a high speed wireless LAN, and to a method of inferring at various places a strength of a wave which is radiated from a wave source such as a radio wave, an acoustic (sound) wave, or the like, and to a method of inferring a three-dimensional spread of multi-path delay waves.
  • a radio electromagnetic
  • a conventional simulation method for multi-path propagation of an in-premise wireless LAN has been a ray-tracing method as shown in J. W. Mcknown and R. L. Hamilton, Jr.: "Ray Tracing as a Design Tool for Radio Networks", IEEE Network Magazine, pp. 27-30, November 1991.
  • this method at a certain receiving point, based on the light receiving directions of direct lights and various reflected lights, each transmitting source from where each light reaches the receiving point without reflection is assumed and then, attenuations and delays are obtained from the distances between these transmitting sources and the receiving point and then interferogram states are obtained.
  • a field strength has been measured under a three-dimensional radio propagation environment by placing a receiver at an observation point.
  • Delay spread is utilized for evaluation of communication quality. For example, a maximum bit rate for the communication is determined from a delay spread value.
  • a radio wave modulated by a PN code is transmitted and the transmitted radio wave is received by a receiver provided at a measuring position and then is measured. Since, in this case, a receiver is also placed at each position to be measured and a direct measurement is performed, a large work load and a long time are necessary. Since a radio wave modulated by PN code is transmitted, a short delay cannot be separated unless the modulation frequency band width is wide enough and thus, the measuring accuracy is low.
  • a first step for observing two-dimensional interferogram data i.e. hologram of a radio wave in a subject space with at least two frequencies is included.
  • the amplitude and the delay of the received wave from each propagation path are measured in step 2 based on the observed data in step 1. Then in step 3, a time response function of each propagation path is generated based on the amplitude, the delay and the directivity characteristic of the receiving antenna. Then, in step 4, this propagation path time response function is convoluted into a modulated carrier signal. Then, in step 5, the convoluted result is multiplied by an unmodulated or non-modulated carrier wave to find a receiving base band signal.
  • a modulated carrier wave signal into which the real part of the time response function is convoluted is multiplied by the in-phase component of the unmodulated carrier wave signal
  • a modulated carrier wave signal into which the imaginary part of the time response function is convoluted is multiplied by the quadrature component of the unmodulated carrier wave signal, and then, these multiplied results are summed to obtain the in-phase component of the receiving base band signal.
  • a vector modulated carrier wave signal is used as the modulated carrier wave signal, in the multiplication of the unmodulated carrier wave signal, the modulated carrier wave signal into which the real part of the Hilbert transformed time response function is convoluted is multiplied by the in-phase component of the non-modulated carrier wave signal, the modulated carrier wave signal into which the imaginary part of the time response function is convoluted is multiplied by the quadrature component of the non-modulated carrier wave signal, and then these multiplied results are summed to find the quadrature component of the receiving base band signal.
  • a modulated carrier wave signal into which the real part of the time response function is convoluted is multiplied by the in-phase component of the unmodulated carrier wave signal having a frequency less than the unmodulated carrier wave signal by an intermediate frequency
  • the modulated carrier wave signal into which the imaginary part of the time response function is convoluted is multiplied by the quadrature component of the unmodulated carrier wave signal having a frequency less than the unmodulated carrier wave signal by an intermediate frequency
  • these multiplied results are summed
  • the summed result is multiplied by an in-phase component of the intermediate frequency carrier wave signal to find an in-phase component of the receiving base band signal
  • the summed result is multiplied by a quadrature component of the intermediate frequency carrier wave signal to find a quadrature component of the receiving base band signal.
  • a frequency selective fading characteristic is obtained from the amplitude and the delay of each received wave and the antenna directivity characteristic.
  • the fading characteristic is then obtained by an inverse Fourier transformation under the limitation of positive frequency range corresponding to the propagation frequency band.
  • the calculation interval for the convolution calculation is made relatively large.
  • the time response function is found as an impulse response in which the amplitude and the delay of each received wave and the antenna directivity characteristic are superposed.
  • the difference between the time when the time response function has a value and the calculation timing is found.
  • the convolution calculation is performed by shifting the phase of the time response function by the difference value.
  • the step 1 uses a radio wave or an acoustic wave etc. in accordance with the subject wave.
  • the hologram is measured at a position where the primary wave source can be viewed from and where the wave space to be inferred can be looked out in the subject space.
  • a wave source image is reconstructed in step 2 using the two-dimensional interferogram data (hologram) measured in step 1. That is, a direction and a strength of each wave source image viewed from the observation plane are obtained.
  • step 3 a propagation delay time of each reconstructed wave source image for the primary wave source is obtained from the phase of the wave source.
  • each wave source is re-positioned in a three-dimensional space using the reconstructed wave source image, the propagation delay time and the phase of the wave source observed by the frequency for the inference.
  • the wave field strength at the observation point is inferred by re-radiating the waves from the re-positioned wave sources and compositing them.
  • step 1 a two-dimensional interferogram data (hologram) is measured at a position where the primary wave source can be viewed from and where the electro-magnetic wave space to be inferred can be looked out. Then in step 2, wave source images are reconstructed using the measured two-dimensional interferogram data (hologram). Then in step 3, a propagation delay time of the reconstructed wave source image for the primary wave source is obtained from the phase of the wave source. Then in step 4, each wave source is re-positioned in a three-dimensional space using the reconstructed wave source image, the propagation delay time and the phase of the wave source observed by the frequency for the inference.
  • hologram two-dimensional interferogram data
  • step 5 the delay time and the strength attenuation amount in accordance with the distance between the receiving point to be evaluated and each re-positioned wave source are obtained. Then in step 6, the delay mean value and the delay spread value are calculated from the delay time and the strength attenuation amount.
  • FIG. 1 is a block diagram showing an arrangement example for measuring two-dimensional interferogram data of waves with respect to a plurality of frequencies in the method of the present invention
  • FIG. 2A is a block diagram showing the generation of a modulated carrier wave signal, a signal that the modulated carrier wave signal has received a fading and a base band signal from these signals in the propagation simulation method of the present invention
  • FIG. 2B is a block diagram showing each process for generating a signal that the modulated carrier wave signal has received a fading and an influence of a receiver characteristic of up to an intermediate frequency, and then for obtaining a base band signal;
  • FIG. 2C is a block diagram showing generation of an orthogonally modulated carrier wave signal, a signal that the orthogonally modulated carrier wave signal has received a fading and its base band demodulated output;
  • FIG. 3 shows an example of a relationship between a sampling pulse and a time response function
  • FIG. 4 is a flow chart showing an example of the process sequence in the radio propagation simulation method of the present invention.
  • FIG. 5 is a flow chart showing an example of the process sequence in the wave field strength measuring method of the present invention.
  • FIG. 6 is a flow chart showing an example of the process sequence in the three-dimensional delay spread measuring method.
  • FIG. 7 is a block diagram showing another arrangement example for measuring two-dimensional interferogram data of waves in the method of the present invention.
  • the radio propagation simulation method will be described in detail with reference to the accompanying drawings.
  • the subject space 11 is observed by dual frequency radio wave hologram (interferogram), i.e., a radio wave hologram of frequency f 1 and a radio wave hologram of frequency f 2 , to measure an amplitude and a delay of a received wave from each propagation path.
  • dual frequency radio wave hologram is described, for example, in H.
  • Kitayoshi et al. "Two-tone CW Complex Holographic Radar Imaging", IEEE AP-S International Symposium Digest, Vol. 3, pp. 1914-1917, June 1993, or H. Kitayoshi "Imaging of Multipath Radio Propagation for 18 GHz Band Wireless LAN System: Applied Radio Holography", IEEE VTC Proceedings, Vol. 2, pp 896-900, June 1994.
  • a radio wave of frequency f 1 and a radio wave of frequency f 2 are radiated from a radiator 12 at a position of a transmission source in the subject space 11.
  • An observation plane 13 is placed at an arbitrary receiving point.
  • a scanning antenna 14 is sequentially placed at various points on the observation plane to receive the radio waves.
  • the radio waves are also received by a fixed antenna 15 provided at a position relatively close to the observation plane 13.
  • Antennas 14 and 15 are the antennas for receiving the radio waves in the same polarization direction as that of the radio waves radiated from the radiator 12.
  • Receiving outputs of the antennas 14 and 15 are passed through pre-amplifiers 16 and 17 respectively. Then unnecessary waves of the receiving outputs are removed in filters 18 and 19 respectively.
  • the filter outputs are frequency mixed with a local signal from a local oscillator 23 in frequency mixers 21 and 22 respectively.
  • Each frequency difference component in the frequency mixed outputs (for example, 21.4 MHz component) is taken out by the respective band-pass filters 24 and 25.
  • Those frequency difference components are further frequency mixed with a local signal (for example, 22.4 MHz signal) of a local oscillator 28 in frequency mixers 26 and 27 respectively.
  • a local signal for example, 22.4 MHz signal
  • Each frequency difference component in the frequency mixed outputs (for example, 1 MHz component) is taken out by the respective low pass filters 29 and 31.
  • the outputs of the filters 29 and 31 are supplied to Fourier integrators 32 and 33 and then sampled respectively by pulses (for example, 10.24 MHz pulses) from an oscillator 34. Each sampled value is converted into a digital signal and then is discrete Fourier integrated.
  • a hologram calculation of the following equation (1) based on the output S r of the Fourier integrator 33 as a reference is applied to the Fourier integration result S m (x,y) of the Fourier integrator 32 to obtain an interferogram data.
  • Oscillators 23, 28 and 34 are synchronized with a stable reference signal (for example, 10 MHz signal) from a reference oscillator 36.
  • a complex hologram (two-dimensional interferogram data) at a time when a radio wave of frequency f 1 is received and a complex hologram at a time when a radio wave of frequency f 2 is received are measured by adjusting the frequency of the local oscillator 23.
  • the size of the observation plane 13 is, for example, 28 ⁇ 28 cm 2 and the moving pitches of the scanning antenna 14 in the x and y directions are, for example, 0.45 cm, respectively.
  • H(x,y) has obtained an amplitude and a phase of the received signal at each point on the observation plane 13 based on the received wave of the fixed antenna 15 as a reference.
  • Two-dimensional Fourier integration of H(x,y) is;
  • ⁇ is an azimuth angle to z axis and ⁇ is an elevation angle to z axis.
  • This I( ⁇ , ⁇ ) provides an amplitude and a phase for each direction viewed from the observation plane 13 and thus provides a reconstruction of radio wave source images.
  • K -1 ( ⁇ , ⁇ ,z) is used as a mere constant. However, if this is differentiated by frequency as shown in the following equation (3), distance information can be obtained.
  • a frequency selective fading characteristic X(f) can be obtained by the following equation (4) from the amplitude a ( ⁇ , ⁇ ) and the delay d( ⁇ , ⁇ ) of the received wave from each direction ( ⁇ , ⁇ ) thus measured at the observation point (x,y) and the directivity characteristic g( ⁇ , ⁇ ) (in the case of non-directivity, the same directional characteristic value for each direction ( ⁇ , ⁇ ) is used) of the antenna to be used.
  • the complex time response x(t) is obtained by an inverse Fourier transform of the fading characteristic X(f) for only positive frequencies using a specific frequency band (f c ⁇ k ⁇ f) as shown in the following equation (5).
  • the reason for multiplying ⁇ f by k is for obtaining the time response including a little outside of the communication band width.
  • This time response is convoluted into the modulated carrier wave signal.
  • the convoluted result is multiplied by the non-modulated carrier wave signal to obtain the demodulated base band signal.
  • a base band modulated signal is passed through a filter 42 from an input terminal 41 to limit the frequency band.
  • the filter output is multiplied by a carrier wave signal R f in a multiplier 43 to obtain a modulated carrier wave signal y(t).
  • the time response i.e., the real part R e x(t)! and the imaginary part I m x(t)! are convoluted into the y(t) in convolution calculation parts 44 and 45 respectively. That is, the following equations (6) and (7) are calculated.
  • the signal is obtained when the y(t) is propagated through the multipath transmission channels determined by the a( ⁇ , ⁇ ), d( ⁇ , ⁇ ), and g( ⁇ , ⁇ ).
  • signals y(t) having received the fading i.e., calculation results of the calculation parts 44 and 45 are multiplied by an in-phase component R f of an unmodulated carrier wave and its quadrature component R f .spsb.* in multipliers 46 and 47, respectively, and then the multiplied results are summed to find a demodulated base band signal R e ⁇ (t)! of a receiver.
  • This R e ⁇ (t)! is represented by the following equation (8).
  • the fading influence of the propagation path can be known from this base band signal ⁇ (t). That is, by such calculations, a radio wave propagation in the subject space 11 of FIG. 1 can be simulated and also, the influence to the propagating signal under multi-path fading can be simulated for various base band signals (signals at the input terminal 41) and the carrier wave signal R f .
  • FIG. 2A shows a transmission simulation for BPSK modulated signal and only the real part of the base band signal ⁇ (t) may be processed.
  • the real part R e x(t)! and the imaginary part I m x(t)! of the propagation path time response are convoluted into the modulated carrier wave signal y(t) which is the output of the multiplier 43 in FIG. 2A, respectively, in the convolution calculation parts 44 and 45.
  • These convolution calculation results are multiplied by an in-phase component and a quadrature component of a signal having a frequency less than the unmodulated carrier wave signal frequency by the intermediate frequency IF in the multipliers 46 and 47, respectively, and then those multiplied results are summed. This summed result corresponds to the intermediate frequency output signal of the receiver.
  • the propagation characteristic including the receiver influence can also be simulated by multiplying this summed result by an in-phase component and a quadrature component of the intermediate frequency signal in the multipliers 48 and 49, respectively, and by passing the multiplied results through base band filters 51 and 52, respectively, to obtain an in-phase component I and a quadrature component Q of the modulated base band signal.
  • This simulation is also one for BPSK modulated signal.
  • the in-phase component I of a modulated signal from an input terminal 41 I is passed through a base band filter 53 and then is multiplied by an in-phase component of a carrier wave signal R f in a multiplier 54
  • the quadrature component Q of the modulated signal from an input terminal 41 Q is passed through a base band filter 55 and then is multiplied by a quadrature component R f .spsb.* in a multiplier 56
  • the multiplied results of the multipliers 54 and 56 are summed to obtain a vector modulated carrier wave signal y(t).
  • This y(t) is supplied to convolution calculation parts 44 and 45, and in convolution calculation parts 57 and 58, the functions that the time response functions x(t) are Hilbert transformed i.e., R e x(t- ⁇ )! and I m x * (t- ⁇ )! are respectively convoluted into y(t).
  • the calculation results in the convolution calculation parts 57 and 58 are multiplied, respectively, by an in-phase component R f and a quadrature component R f .spsb.* of a non-modulated carrier wave signal in multipliers 61 and 62.
  • multiplied results are summed and then the summed result is supplied to a base band filter 52 to obtain a signal corresponding to a quadrature component Q of a demodulated base band signal of a receiver.
  • the multiplied results in the multipliers 46 and 47 are summed and then the summed result is passed through a base band filter 51 to obtain a signal corresponding to an in-phase component I of the demodulated base band signal of the receiver.
  • the input of a base band filter 52 is represented by the following equation (9);
  • a carrier wave frequency used in the simulation of calculation has been caused to correspond to a carrier wave frequency actually used by defining as follows:
  • f c is an actual carrier wave frequency
  • the carrier wave frequency f c ' used in the simulation of calculation can be set to a frequency lower than the actual carrier frequency f c . That is, the following equations are given.
  • a quickly changing modulated wave signal can be converted to relatively low frequency signal, and consequently, a relatively faithful simulation of propagation signal wave form can be performed by a slow sampling frequency (relatively long calculation time interval), i.e., less calculation volume.
  • a slow sampling frequency relatively long calculation time interval
  • the frequency band of the modulated carrier wave signal is wider as in CDMA (code division multi-access)
  • the frequency band cannot be limited.
  • calculation volume could be reduced as described below.
  • An impulse response is obtained by the following equation (11) as a time response function x(t) of a propagation path.
  • ⁇ is performed on k and the range of k is all the observation time range.
  • ⁇ (n ⁇ t) of the equation (12) is a received signal of a modulated carrier wave signal.
  • the impulse response is obtained by the equation (11) and then the radio propagation simulation can be performed using the time response function x(t) as shown in FIGS. 2A, 2B or 2C.
  • the time response function x(t) can be converted like the equation (13) to reduce the calculation volume.
  • FIG. 4 shows a process sequence in the aforementioned radio propagation simulation method of the present invention. That is, two-dimensional interferogram data in a subject space are measured with respect to frequencies f 1 and f 2 respectively (step S 1 ). Then, a radio wave source image is reconstructed from each interferogram data (step S 2 ). Then a time response function x(t) of the propagation path is obtained based on an amplitude a( ⁇ , ⁇ ) and a delay d( ⁇ , ⁇ ) of the radio wave at an observation point from each reconstructed wave source image and a directivity characteristic g( ⁇ , ⁇ ) of the used receiving antenna (step S 3 ).
  • the obtained x(t) is convoluted into a modulated carrier wave signal y(t) (step S 4 ).
  • the equations (12) and (13) may be used.
  • the convoluted result is demodulated to the base band signal (step S 5 ).
  • the base band signal may be obtained immediately by detecting the carrier wave of the convoluted result, or the base band signal may be obtained, after the intermediate frequency conversion, by detecting the intermediate frequency.
  • two-dimensional interferogram data of the electromagnetic waves are measured using at least two frequencies at the position where the primary wave source can be viewed from and where the electro-magnetic field space to be inferred can be looked out.
  • a radiator 12 for radiating a radio wave of frequency f 1 and a radio wave of frequency f 2 as a primary wave source in the subject space 11 is used.
  • An observation plane 13 is placed at the position where the radiator 12 can be viewed from and where the electromagnetic field space to be inferred can be looked out.
  • the two-dimensional interferogram data (complex hologram) measurement after that is the same as that described above. That is, a complex hologram H(x,y) can be obtained from a hologram calculation part 35. Then, as in the previous case, this H(x,y) is two-dimensional Fourier integrated to reconstruct the radio wave source image.
  • each propagation delay time of the wave from the radiator 12 which is a primary wave source of the reconstructed wave source image is obtained from the phase of the wave source.
  • the reconstructed wave source image i.e., the propagation delay time D( ⁇ , ⁇ ) between the secondary wave source and the primary wave source viewed from the observation plane is obtained by the following equation (15).
  • the wave source given by the equations (19) and (20) exists on each position in the three-dimensional space determined by the reconstructed image coordinate ( ⁇ , ⁇ ), namely, on the coordinate X, Y, Z given by the equations (16), (17) and (18).
  • the complex electric field E(x',y',z', ⁇ ) including the electric field strength and the phase at an arbitrary position of the three-dimensional space viewed from the hologram observation plane is inferred by the following equation (21) which composites the waves from all the wave sources including the primary wave source.
  • ⁇ '( ⁇ , ⁇ ) is a distance from a position (x',y',z') to each wave source and is expressed by the following equation (22). ##EQU2##
  • FIG. 5 briefly shows the above process steps. That is, the process steps S 1 and S 2 in FIG. 4 are similarly performed to reconstruct the wave source images. Then in this embodiment, a propagation delay time D( ⁇ , ⁇ ) of each wave source image to the primary wave source 12 is obtained by the equation (15) (step S 6 ). Then, each wave source is re-positioned to an absolute coordinate (X,Y,Z) (step S 7 ). The electric field strength and the phase at an arbitrary position in the absolute coordinate are composited by the equation (21) with respect to the electro-magnetic wave from the re-positioned wave source (step S 8 ).
  • a radiator 12 for radiating a radio wave of frequency f 1 and a radio wave of frequency f 2 as the primary wave source is used in FIG. 1.
  • An observation plane 13 is positioned at a position where the radiator can be viewed from and where the electro-magnetic field space to be inferred can be looked out.
  • Each two-dimensional interferogram data H(x,y) of radio waves of frequencies f 1 and f 2 is obtained and then the radio wave source image is reconstructed.
  • each propagation delay time D( ⁇ , ⁇ ) of the reconstructed secondary wave source image to the radio wave of the primary wave source is obtained.
  • each wave source is re-positioned to an absolute coordinate (X,Y,Z) using this D( ⁇ , ⁇ ), the reconstructed wave source image I( ⁇ , ⁇ )exp ⁇ j ⁇ ( ⁇ , ⁇ ) ⁇ and the phase of the wave source observed by a frequency f to be inferred.
  • the wave source position is given by the equations (16)-(18) and the radiation strength of the wave source I'( ⁇ , ⁇ , ⁇ ) and the phase ⁇ '( ⁇ , ⁇ , ⁇ ) are given by the equations (19) and (20), respectively.
  • a mean delay value m and a standard deviation ⁇ rms of the delay of a radio wave from each wave source at an arbitrary position (x',y',z') in a three-dimensional space (X,Y,Z) are obtained, respectively, by the following equation (23) and (24) based on the delay time ⁇ '( ⁇ , ⁇ )/c and the strength ⁇ I'( ⁇ , ⁇ , ⁇ )/ ⁇ ( ⁇ , ⁇ ) ⁇ 2 in accordance with the distance ⁇ '( ⁇ , ⁇ ) between the position (x',y',z') and each wave source.
  • the mean delay value ⁇ m and the standard deviation ⁇ rms of the delay at the arbitrary position (x', y',z') in the three-dimensional space viewed from the hologram observation plane 13 are obtained by calculating the equations (23) and (24), respectively.
  • a delay wave spread amount is a squared value of the value ⁇ rms obtained by the equation (24).
  • the value ⁇ rms of the equation (24) may sometimes be referred to as the delay spread.
  • a usual radio wave communication is performed using a finite frequency band. Therefore, in the finite frequency band range of ⁇ , the variations of strength I' ( ⁇ , ⁇ , ⁇ ) and phase ⁇ ' ( ⁇ , ⁇ ) of each wave source are considered to be small.
  • the strength is I'( ⁇ , ⁇ )
  • the phase is ⁇ '( ⁇ , ⁇ )
  • the antenna directivity is A( ⁇ , ⁇ )
  • the frequency response of a propagation path at an arbitrary position (x',y',z') can be obtained by the following equation (25).
  • the mean delay ⁇ m and the standard deviation of delay ⁇ rms at an arbitrary position are obtained by the following equations (27) and (28), respectively, from this time response function.
  • FIG. 6 shows a process sequence for inferring ⁇ m and ⁇ rms .
  • the process up to the re-positioning of each wave source to an absolute coordinate is the same as that in the embodiment of the electro-magnetic field strength inference method. That is, the process of the steps S 1 , S 2 , S 6 and S 7 is performed and then, the mean delay ⁇ m is obtained by the equation (23) or (27) and the standard deviation ⁇ rms is obtained at an arbitrary position (x', y',z') by the equation (24) or (28) from the delay time and the strength in accordance with the distance ⁇ '( ⁇ , ⁇ ) from each wave source (step S 8 ).
  • the complex hologram (two-dimensional interferogram data) H(x,y) can also be obtained by the integration in the time region instead of in the spectrum region.
  • FIG. 7 where the same reference symbols are assigned to the portions corresponding to those in FIG. 1.
  • a base band signal from a low pass filter 29 is supplied to multipliers 64 and 65.
  • the output of a band pass filter 25 of the fixed antenna 15 side which is a reference is multiplied in a multiplier 67 by an output of a local oscillator 28 shifted by ⁇ /2 in a phase shifter 66.
  • a base band signal is taken out by a low pass filter 68 from the multiplied output.
  • the outputs of the low pass filters 31 and 68 are supplied to multipliers 64 and 65 respectively. That is, the output of the band pass filter 25 is orthogonally detected or undergoes a quadrature-detection. The in-phase component and the quadrature component of the detected output are multiplied by the base band signal from the band pass filter 29 in the multipliers 64 and 65, respectively.
  • the outputs of the multipliers 64 and 65 are sampled by the clock from the oscillator 34 in integrators 71 and 72, respectively, to form time series digital signals. Then, those signals are integrated in the time region and are supplied to a calculation part 73 as a real part R e and an imaginary part I m , respectively.
  • the outputs of the low pass filters 31 and 68 are branched respectively to squaring parts 74 and 75 and squared therein, respectively. Then, the squared signals are summed in a summing and square root extraction part 76. The summed result is square root extracted to obtain the magnitude of the received output
  • of the fixed antenna and then supplied to the calculation part 73. In the calculation part 73, the calculation of R e +jI m S m ⁇ S r .spsb.* is performed and then this calculation result is divided by
  • a radio wave of circular polarization is radiated from the radiator 12.
  • the horizontal polarized wave is received at the scanning antenna 14 and the fixed antenna 15 to obtain the radio wave hologram H H (x,y).
  • the vertical polarized wave is also received to obtain the radio wave hologram H v (x,y).
  • complex weighing factors ⁇ H and ⁇ H are selected to obtain the radio wave hologram H'(x,y) of an arbitrary polarized wave by the following equation.
  • I( ⁇ , ⁇ ) is found for H'(x,y) as mentioned above and the time response function of the propagation path is obtained. Then, the radio propagation simulation can be similarly obtained. Or, otherwise the position, the radiation strength and the phase of each wave source in the three-dimensional absolute coordinate are obtained and then a complex electric field E(x',y',z', ⁇ ) at an arbitrary position, or a mean delay ⁇ m of a radio wave from each wave source and its standard deviation ⁇ rms can be obtained.
  • the interferogram data H'(x,y) of an arbitrary polarized wave can be obtained by the following equation.
  • ⁇ H and ⁇ v are selected to obtain the desired interferogram data H'(x,y). Then, an electric field strength at an arbitrary position (x',y',z') could be obtained by reconstructing the secondary wave source image using the interferogram data.
  • a receiving antenna directivity A( ⁇ , ⁇ ) may be superposed on the receiving electric field strength at an arbitrary position (x',y',z') for weighted composition. That is, this result may be obtained by calculating the following equation.
  • the received output of the receiving diversity can be inferred by the composition of E(x 1 ',y 1 ',z 1 ', ⁇ ) and E(x 2 ',y 2 ',z 2 ', ⁇ ) or the selection of larger strength of the E(x 1 ',y 1 ',z 1 ', ⁇ ) and E(x 2 ',y 2 ',z 2 ', ⁇ ).
  • E'( ⁇ , ⁇ , ⁇ ) ⁇ 1 E(x 1 ',y 1 ',z 1 ', ⁇ )+ ⁇ 2 E(x 2 ',y 2 ',z 2 ', ⁇ ) is calculated.
  • ⁇ ⁇ (x 1 '-x 2 ') 2 +(y 1 '-y 2 ') 2 +(z 1 '-z 2 ') 2
  • ⁇ (x 1 ,y 1 ,z 1 )
  • ⁇ 1 , ⁇ 2 are the complex weighing factors, respectively, which are determined such that the composite electric field strength E' ( ⁇ , ⁇ ) is optimized.
  • the radiated radio waves f 1 and f 2 only the unique word portion from an actually operating radio station whose location is known may be taken out and utilized, or the switching information of a channel central frequency in the frequency hop TDMA may be utilized. That is, for example, since the code of the unique word portion is already known, the frequencies f 1 , and f 2 of the modulation spectrum shift can be separately received and the respective interferogram data H(x,y) may be generated.
  • the wave field strength inference method of the present invention can also be applied to the strength inference of each portion not only in radio propagation field but also in acoustic propagation field.
  • the radio wave holograms on at least two frequencies are observed.
  • the amplitude and the delay (with PS resolution) of the received wave are found.
  • the time response function of each propagation path is found from the amplitude, the delay, and the receiving antenna characteristic. Since this time response function is convoluted into the modulated carrier wave signal, that is, since the time response function is obtained by an actual measurement, when, for example, the propagation path is separated into 4096 paths in the indoor region, several ten multi-paths existing within 1 ns of time duration can be separated even if many complex reflection objects are complicatedly arranged and many complex paths are generated.
  • the electric field distribution at the observation plane is accurately reflected and the time response function can be accurately found. Consequently, the radio propagation can be accurately simulated.
  • a simulation as to what a receiving demodulated signal is obtained can be performed.
  • the present invention can be applied to the simulation of a high speed wireless LAN (19 GHz band, 200 Mbps) including the antenna system and the modulation/demodulation system.
  • secondary wave sources are reconstructed from wave interferogram data (complex hologram). These wave sources are re-positioned in a three-dimensional absolute space and these waves are composited at an arbitrary position to infer the strength and the phase. Therefore, each position is not necessary to be measured by a sensor and there is no influence by the sensor moving equipment. Consequently, the precise inference of the wave field distribution can be performed.
  • a transmitted radio wave in an existing communication system can be utilized to measure the electric field distribution in the radio propagation space of the communication system.
  • changes in configuration or other changes such as a construction/demolition of a building occur in the radio propagation space after the start of the communication system, it is possible to measure the change of the electric field distribution and to improve the failure state of the communication system by following the change.
  • the interferogram data (complex hologram) are observed, the wave source images are reconstructed and are re-positioned in a three-dimensional absolute space. Since the attenuation and the delay in accordance with the distance between each wave source and an arbitrary position which can be viewed from the hologram observation plane are found to obtain a mean delay ⁇ m and standard delay deviation ⁇ rms , those values can be obtained simply and in short time compared with the prior art in which a receiver is moved to the respective positions to be measured. In addition, in the case of the present invention, no special modulation is necessary. Therefore, the measurement can be performed in a narrow band and a short delay can also be separated.

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JP849595A JPH08204590A (ja) 1995-01-23 1995-01-23 電波伝搬シミュレート方法
JP7-008497 1995-01-23
JP00849795A JP3570572B2 (ja) 1995-01-23 1995-01-23 ３次元遅延分散推定方法
JP7-008495 1995-01-23
JP00849695A JP3570571B2 (ja) 1995-01-23 1995-01-23 波動場強度推定方法
JP7-008496 1995-01-23
PCT/JP1996/000110 WO1996023363A1 (fr) 1995-01-23 1996-01-23 Procedes de simulation de la propagation d'ondes radio, d'estimation de l'intensite d'un champ d'onde et d'estimation d'une dispersion de retard a trois dimensions

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